Method of controlling energization of electro-magnetically driven valve with variable feedback gain

ABSTRACT

A control method with variable feedback gain for energization of an electro-magnetically driven intake/exhaust valve of an internal combustion engine increases opening and closing speeds of the intake/exhaust valve driven with electromagnets having small capacity and brings the final speed of the opening and closing action of the valve close to zero. A target moving speed of the armature relative to the electromagnets is determined dependent upon a spacing distance of the armature from the electromagnet; at least a part of energization of the electro-magnetically driven valve is controlled through feedforward control so as to make an actual moving speed of the armature relative to the electromagnets in conformity with the target moving speed while at least the other part of the energization is controlled through feedback control based upon a deviation of the actual moving speed from the target moving speed.

BACKGROUND OF INVENTION

1. Technical Fields

This invention relates to methods of controlling energization of anelectro-magnetically driven valve such as an intake valve and an exhaustvalve in an internal combustion engine.

2. Prior Art

With the recent development of computer control technologies, in thefield of internal combustion engines, especially for a vehicle, anelectro-magnetic actuator has been employed for opening and closing anintake valve and/or an exhaust valve, instead of a conventional cam on acam shaft driven synchronously with a crank shaft, and, based upon theincrease of the degree of freedom of the timing of the opening andclosing operations of the valves through use of the electromagneticactuator, there have been proposed various manners of controlling theoperation of an internal combustion engine. Examples of such operationcontrols are described in Japanese Patent Laid-Open publications Nos.11-210916, 2000-73800, 2000-234534, 2000-337177, 2001-182570,2001-193504, 2002-81329, 2002-81569.

FIG. 1 in the accompanied drawings shows a general and schematicsectional view of an electro-magnetically driven intake valve, which issimilarly shown in FIG. 2 of the Japanese Publication No. 2001-193504based upon an application filed by the same applicant as the presentapplication. In this drawing, an opening end of an inlet port 26 isfringed with a valve seat(s) 200 and opened and closed by a valve body28 a. The valve body 28 a is carried by a valve shaft 28 b, and in thisfigure, a valve guide 201 guides the valve shaft 28 b so that the valveshaft can move up and down, and thereby, the valve body 28 a is movedbetween opened and closed positions by electromagnetic driving apparatusgenerally denoted by 30.

The electromagnetic driving apparatus 30 has a housing 300, within whichincorporated are a valve-closing electromagnetic apparatus consisting ofvalve-closing cores 301 and valve-closing coils 303; a valve-openingelectromagnetic apparatus consisting of valve-opening cores 302 andvalve-opening coils 304; an armature 305 carried on the valve shaft 28 band movable between the valve-closing and valve-opening electromagneticapparatuses; and compression coil springs 306 and 307. As shown in thedrawing, the compression coil springs 306 and 307 bring the armature 305to an intermediate position between the two electromagnetic apparatuseswhen neither of coils 303, 304 is energized.

In the example as shown here, an intake valve lift sensor 40 is mounteddirectly on the electromagnetic driving apparatus 30. This lift sensorhas a housing 400, mounted on the housing 300 of the electromagneticdriving apparatus 30; a disk-like target 401, mounted on the upper endof the valve shaft 28 b within the housing 400; and a gap sensor 402attached on the housing 400, while facing on the target 401, anddetecting the displacement of the target.

Further, although not shown in the drawing, in such anelectro-magnetically driven valve used as intake and/or exhaust valves,in general, a slip joint is incorporated near the lower end of the valveshaft 28 b, namely the coupling portion with the valve body 28 a, whichslip joint enables the distance between the valve body and armature toexpand and contract very slightly. This slip joint is provided foravoiding a condition that, if the armature is fixedly connected to thevalve body, the support of the armature flush against the valve-closingcores 301 and coils 303 would prevent the tight sealing of the valvebody to the valve seat, when the valve body is forced on the valve seatby the pressure within a cylinder during compression and explosionstrokes.

The control of operation of opening and closing this type ofelectro-magnetically driven valves is done by controlling energizationof valve-opening and/or valve-closing coils. In this case, generally,the operational states of an electro-magnetically driven valve, used foreither of an intake valve or an exhaust valve, are either of an openstate or a close state, and any states in between are transient unlessany special control of opening and closing a valve is done. Thus,usually, an electro-magnetically driven valve, when operated, is held ineither of a full opened position, in which an armature is adhered to anvalve-opening electromagnet consisting of valve-opening coils and cores,or a full closed position, in which the armature is adhered to anvalve-closing electromagnet consisting of valve-closing coils and cores,by feeding a weak holding current to the valve-opening or valve-closingcoils except during opening or dosing the valve. When the valve body ismoved from the full dosed position to the full opened position, theholding current for the valve-dosing coils is turned off first (usually,a reverse current is subsequently fed to the valve-dosing coils), andthen, under the action of springs, the valve body and armature startmoving to the valve-opening side in unison. Thereafter, when thearmature reaches to a position near an intermediate point between thevalve-opening and valve-dosing electromagnets and the distance betweenthe armature and valve-opening electromagnet is shorten enough for thevalve-opening electromagnet to function effectively through energizationof the valve-opening coils, the energization of the valve-opening coilis started. Similarly, the valve is moved from the full opened positionto the full closed position.

In general, when a valve body is started to move from a full closedposition to a full opened position or from the full opened position tothe full closed position, its moving speed increases gradually togetherwith its displacement (Usually, as an armature moves closer to anelectromagnet, its electromagnetic force attracting the armatureincreases.). Preferably, however, the moving speeds of the valve bodyand armature is to be reduced to almost zero by the end of the openingor closing operation of the valve, for avoiding violent collision of thearmature against the coils and cores of the valve-opening and/or dosingelectromagnets at the end of the opening or closing operation of thevalve body; and violent collision of the valve body against a valve seatin dosing the valve. On the other hand, in order to complete the openingand closing operation of the valve quickly, preferably, the movingspeeds of the valve body and armature are to be increased in theintermediate portion of the opening and closing movement of the valve.

From the above, it is generally recognized that the moving speed of avalve body or an armature is preferably to be varied with thedisplacement of the valve body or armature as shown in FIG. 2. In FIG.2, an example of speed change in opening a valve is shown, wherein theabscissa is the displacement of a valve body or armature, namely Lift(the distance between the valve body and valve seat) and the ordinate isan opening speed, namely, the moving speed of the armature or valve bodyduring opening. For varying the moving speed with lift as shown in FIG.2, exciting current to be fed to coils (valve-opening coils in thiscase) is made varied with the position of the valve body or armaturealong a profile as shown in FIG. 3.

In this connection, mathematically speaking, the concepts defined as“distance”, “movement” and “speed” each have positive and negativevalues, and in matters of the opening and closing of a valve as in thepresent application, the distance, movement and speed are regarded aspositive or negative, depending upon the direction of the movement of avalve body; but, since the present objects are to consider how openingand/or closing operations of a valve body are made quick and how themovement of the valve is terminated at the end of the operation withoutimpact, the displacement of the valve body or armature, represented withlift as shown above, and the moving speed of the valve body or armaturein the direction of increasing the displacement are defined as positive.

Furthermore, in order to obtain the relation between the displacementand moving speed of a valve body or an armature as shown in FIG. 2,exciting current fed to coils is controlled in connection with thedisplacement through combination of a feedforward(FF) control and afeedback (FB) control. In this case, first, the exciting current iscontrolled with the FF control for setting an actual moving speed for atarget moving speed as shown in FIG. 2 (the profile in FIG. 3). Adeviation of an actual moving speed from the target, when generated, is(expectedly) cancelled by correcting the exciting current through the FBcontrol based upon the value of the deviation. Usually, based upon adeviation of an actual moving speed V from a target moving speed Vt, ΔV(=V−Vt), an amount of FB control for exciting current is given by−Gb·ΔV, where Gb is a positive FB control gain. Thus, when ΔV ispositive, namely, when the actual moving speed exceeds the target movingspeed, the control of the exciting current is done by subtracting Gb·ΔVfrom the corresponding FF control amount. In one case, an FB controlgain Gb is constant, and in other cases as described in the above JP No.2000-23454, an FB control gain is increased as the distance of spacingbetween an armature and an electromagnet attracting the armature(spacing distance) increases. In JP No. 2002-81329, it is proposed todefine fields in accordance with the ranges of deviation ΔV and spacingdistance and to execute a feedback control using a different FB controlgain for each of the fields.

By the way, since an FB control amount is given by −Gb·ΔV as describedabove, it can be understood that, the larger the FB control gain is, thehigher responsibility or sensitivity of the control, namely, the highercontrol speed is obtained, thereby increasing the effect of the FBcontrol. The increase of the control speed, however, often causes anexcessive control inducing hunting in the control. On the other hand, ifan FB control gain is excessively small, the longer time would berequired for making an actual moving speed in conformity with a targetmoving speed, or the moving speed at the end of the movement would notreach to the target moving speed that would be an appropriate value.

Further, in the speed control of the opening and closing operation of anelectro-magnetically driven valve: the controlled object of the presentinvention, the importance and/or necessity of FB control varies,dependent upon the relation between actual and target moving speeds,such as the direction and magnitude of the deviation between the actualand target moving speeds. As already described, in order to preventviolent collision between a valve seat or an electromagnet and a valvebody or an armature resting thereon (at the end of an opening or closingoperation), a target moving speed is so set that the speed at theresting becomes substantially zero. For example, however, in a case thatan actual moving speed exceeds its target value, it is enough that thespeed at the resting is within a certain satisfactory range and there islittle need to urgently correct the actual moving speed through FBcontrol (it is possible that the reduction in the time for opening andclosing a valve is preferable.). On the other hand, when an actualmoving speed is lower than its target one, it is possible that themoving speed has become zero before an armature reaches toelectromagnets. In this case, the armature will be pulled back bysprings, and thereby, the armature and a valve body are floating aroundthe intermediate position between opened and dosed positions, inducing avery serious problem of stepping-out of operation of an intake valve oran exhaust valve. In order to avoid such a stepping-out condition, it isrequired that an actual moving speed can be corrected quickly through FBcontrol without inducing the control hunting.

Accordingly, in the control of opening and closing speed of anelectro-magnetically driven valve, an FB control gain should be settaking into account the necessity of FB control based upon the relationbetween actual and target moving speeds so as to avoid the controlhunting and stepping-out condition.

Further, it is possible that a target moving speed or an FF controlamount (current fed to electromagnets If given in accordance with theprofile in FIG. 3) does not match characteristics of an actualelectro-magnetically driven valve due to aging variation of the valve oran individual difference of products, and thereby, the magnitude(absolute value) of an FB control amount would be enlarged. In otherwords, while a target moving speed and/or an FF control amount ispredetermined values based upon the characteristics of anelectro-magnetically driven valve, it is possible that the predeterminedtarget moving speed would turn incompatible with the characteristics ofan actual valve because the actual valve has a plurality of frictionalsliding portions, electromagnets, springs, etc., the conditions andcharacteristics of which elements can vary from those at themanufacturing thereof. Also, in actual products, some differences ofperformances among the products are inevitable so that a target movingspeed predetermined based upon designed characteristics can beincompatible with actual characteristics of a valve. Then, it would bedifficult to make an actual moving speed in conformity with its targetmoving speed, resulting in the increase of the deviation ΔV andconsequently, the increase of an FB control amount. This, in turn, wouldincrease the fear of occurrence of the control hunting as describedabove. Accordingly, in order to reduce the fear of the hunting due to FBcontrol and to make an actual moving speed in conformity with its targetvalue quickly, it is preferable that a target moving speed and/or an FFcontrol amount can be corrected, compensating for aging variation of anelectro-magnetically driven valve and the other conditions thereof.

Further, while a function determining (calculating) an FB control gainGb is set out upon manufacturing or designing an electro-magneticallydriven valve, it is possible that an FB control amount is insufficientto make an actual moving speed in conformity with its target movingspeed because of aging variation and/or individual differences amongproducts, as described above. Thus, it is preferable that a functionand/or means for determining FB control gain Gb can be correctedappropriately after starting of use of an electro-magnetically drivenvalve.

Moreover, during use of an internal combustion engine, intake/exhaustvalves are directly exposed to pressure variation of operational fluidin cylinders, and thus, the movements of valve bodies are subject toacceleration and deceleration forces from the operational fluid.Acceleration and deceleration forces are advanced by first order from amoving speed to be controlled, and accordingly, are not directlyreflected in −Gb·ΔV. Thus, more appropriate speed control will beachieved if effect of pressure of operational fluid is taken intoaccount in control of an FB control gain.

Furthermore, as already noted, in the energization control forelectro-magnetically driven valves described in some of the above-listedpatent publications, it has been proposed to selectively andappropriately employ different FB control gains depending upon thedistance between an armature and (energized) electromagnets or deviation(ΔV) between an actual moving speed and a target moving speed, ratherthan an always constant FB control gain. In order to avoid the controlhunting and/or stepping-out of control, however, it is desirable thatdeviation ΔV or else is corrected quickly and gently without abruptchange of an FB control gain.

SUMMARY OF INVENTION

The objects of the present invention are to provide methods ofcontrolling energiazation for improving the performance of anelectro-magnetically driven valve operating as an intake or exhaustvalve for an internal combustion engine, wherein, for increasing openingand closing speeds of the valve by increasing a control speed in theopening and closing control of the valve, there are taken into accountthat the importance of FB control varies dependent upon the relationbetween an actual moving speed and its target; and that there are theparticular directional characteristics in the hunting and stepping-outlimiting the gain of the FB control which consists in the whole control,as noted above; and also the effects of aging variation, etc. in thecontrol of the electro-magnetically driven valve.

For achieving the above-mentioned object, the present invention providesa method of controlling energaization of an electro-magnetically drivenvalve having electromagnets and an armature which is attracted to theelectromagnets and thereby moving a valve body to either of an openedposition or a closed position, comprising: determining a target movingspeed of the armature relative to the electromagnets dependent upon aspacing distance of the armature from the electromagnet; controlling atleast a part of energization of the electro-magnetically driven valvethrough feedforward control so as to make an actual moving speed of thearmature relative to the electromagnets in conformity with the targetmoving speed while controlling at least the other part of theenergization through feedback control based upon a deviation of theactual moving speed from the target moving speed; in which a gain of thefeedback control is changed based upon a relation between the actualmoving speed and the target moving speed.

In the above-described energization control method of theelectro-magnetically driven valve, the FB control gain may be smallerwhen a force of operational fluid that the electro-magnetically drivenvalve controls acts on the valve body in the same direction as themovement of the valve body than when a force of the operational fluidacts in the direction opposite to the movement of the valve body.

In the above-described energization control method of theelectro-magnetically driven valve, the feedback control gain may bechanged smaller when the actual moving speed is higher than the targetmoving speed than when the actual moving speed is lower than the targetmoving speed.

Further, when a final value of the actual moving speed (a resting speed)is smaller than a predetermined speed threshold, the energization amountof the electromagnets may be shifted through learning modification so asto increase the moving speed for the spacing distance. Here, thelearning modification means modification of a current and future controlbased upon a result of an already executed control.

Furthermore, when a deviation of an actual moving speed from a targetmoving speed is not lower than a predetermined deviation threshold and afinal speed of the movement of the armature is not lower than apredetermined speed threshold, the calculation of the FB control gainmay be shifted to be increased through learning modification.

Moreover, when a deviation of an actual moving speed from a targetmoving speed is entirely not higher than a predetermined deviationthreshold but a final speed of the movement of the armature is not lowerthan a predetermined speed threshold, the energization amount of theelectromagnets may be shifted through learning modification so as todecrease the moving speed at least around the end of the movement.

Also, the feedback control gain may be controlled to vary continuouslydepending upon a deviation of an actual moving speed from a targetmoving speed.

In this connection, learning modification may be done in such a mannerthat a target moving speed of an armature is set out depending upon thespacing distance of the armature from an electromagnets; and then, theenergization of an electro-magnetically driven valve is controlled so asto bring an actual moving speed of the armature relative to theelectromagnets in conformity with the target moving speed, in which thesetting of the target moving speed is modified through learningmodification based upon a deviation of the actual moving speed from thetarget moving speed.

As described above, in a control of energization of anelectro-magnetically driven valve including FF control, where a targetmoving speed of an armature relative to electromagnets is set out for aspacing distance of the armature relative to the electromagnets and theenergization of the electromagnets is controlled so as to bring theactual moving speed in conformity with the target moving speed, and FBcontrol, where the energization of the electromagnets is correcteddepending upon the deviation of the actual moving speed from the targetmoving speed, the necessity of the FB control varies depending upon therelation between the actual moving speed and target moving speed.Accordingly, by setting the FB control gain based upon the relationbetween the actual moving speed and target moving speed, a moreappropriate control of the moving speeds of the valve body and armaturecan be achieved.

In particular, as already noted, since the risk of occurrence of thestepping-out condition is higher when an actual moving speed of anarmature is lower than its target moving speed (ΔV<0) than when theactual moving speed is higher than its target moving speed (ΔV>0), evenif the absolute values of the deviations of the actual moving speed fromthe target moving speed in both the cases are equal to each other, it isrequired in the former case to increase the moving speed as quickly aspossible. Thus, when the actual moving speed of the armature is lowerthan the target moving speed, the FB control gain will be set higher forbringing the actual moving speed close to the target moving speed, andon the other hand, when the actual moving speed is higher than thetarget moving speed, the FB control gain will be set smaller than thatin the case that the actual moving speed of the armature is lower thanthe target moving speed, while avoiding the occurrence of the controlhunting, and thereby it is allowed to bring the actual moving speed inconformity with the target moving speed while surely excluding the fearof the stepping-out in the opening and closing control of theelectro-magnetically driven valve.

Further, as already noted, a force of intake and/or exhaust flow actingon a valve body will help the action of electromagnets attracting anarmature if the force is in the same direction as the movement of thevalve body, but oppose the attraction of the electromagnets for thearmature if the force is in the opposite direction to the movement ofthe valve body. Thus, the effect of the operational fluid can beeliminated from the energization control of the electro-magneticallyvalve through modification of an FB control gain depending upon thedifference of the force impacted on the valve body from the operationalfluid, in which modification the FB control gain is set smaller when aforce of an operational fluid that the electro-magnetically driven valvecontrols acts on the valve body in the same direction as the movement ofthe valve body than when the force of the operational fluid acts in theopposite direction to the movement of the valve body.

Also, the problem that characteristics of an actual electro-magneticallydriven valve turn to be incompatible with predetermined FF controland/or FB control can be solved through learning modification of controlamounts, namely modifying current and future operation based uponresults of past operation automatically and anytime in each of products.

One of important matters to be modified through such learningmodification is that, with reference to the graph of opening speed vs.lift as shown in FIG. 2, the curve of an actual movement of an armatureat and around its end should not fall below the target curve (In FIG. 2,although the resting speed (at full opened position) is shown assubstantially zero, the armature in practical contacts theelectromagnets at a low speed within a range of inducing no damage onelectromagnets). If the curve of the actual moving speed of the armaturearound its end falls below the target curve, the possibility that thespeed becomes substantially zero before the armature reaches to thepoint of full opening would increase. In this case, electromagneticforce must be increased by, for instance, applying a rather high holdingcurrent instantly the speed falls down to zero; otherwise, the armaturewould be pulled back to an intermediate point due to the action ofsprings, resulting in failure in adhesion of the armature, and possiblycausing the above-mentioned stepping-out condition.

Thus, as described above, through learning modification where anenergization amount fed to electromagnets is shifted so as to increase amoving speed when a final value of an actual speed is smaller than apredetermined speed threshold, the final value of the actual movingspeed is always maintained at or above a predetermined speed threshold,and thereby it can be avoided that the actual moving speed falls to zerobefore reaching the full opening point. In this case, it is enough thatthe predetermined speed threshold is set as small as possible and withinsuch a range that any control errors and/or control fluctuation couldnot render the actual moving speed fallen down to zero erroneously.

The learning modification is also desired in a condition that an actualmoving speed exceeds a target moving speed; the deviation of the actualmoving speed from the target moving speed is not lower than apredetermined deviation threshold; and a final speed of the movement ofthe armature is also not lower than a predetermined speed threshold. Itmay be estimated that such a condition will occur because anenergization amount fed to electromagnets for the target moving speed istoo high. In such a condition, through modifying a function ofcalculating an FB control gain so as to increase the FB control gain;reducing the energization amount fed to the electromagnets; andmodifying downwardly the actual moving speed relative to the targetmoving speed over the whole movement, it can be simultaneously overcomethat both the problems that the actual moving speed would increaserelative to the target moving speed and that the final speed of themovement of the armature is too high.

Further, the learning modification is also desired in a condition that,although a deviation of an actual moving speed from a target movingspeed is entirely at or below a predetermined deviation threshold, afinal speed of the movement of the armature is at or above apredetermined speed threshold. Such an operational condition means thatthe setting of exciting current fed to coils is deviated to the higherspeed side at the end of the movement. Thus, in such a condition,through learning modification, the energization amount fed to theelectromagnets is shifted downwardly so as to reduce the moving speed atleast at and around the end of the movement.

Moreover, when a FB control gain is substantially continuously changeddepending upon a deviation ΔV, an FB control amount in the direction ofcanceling the deviation ΔV will continuously vary without abrupt changeand gradually increase and/or decrease depending upon the deviation ΔV.Accordingly, not only the deviation ΔV will disappear more quickly,compared with the case of employing a constant FB control gain, but alsothe fear of occurrence of the control hunting will be reduced because ofabsence of an abrupt change in the FB control amount, which would beseen in a case of a stepwise changed. FB control gain (in a certaincase, it is possible that the sign of the FB control amount isreversed).

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 schematically shows a section of an example of a structure of anelectro-magnetically driven intake valve and an intake valve lift sensormounted thereon.

FIG. 2 is a graph showing the relation of lift vs. opening speed duringopening an electro-magnetically driven valve as a preferable relationbetween a position and a moving speed of an armature in the valve.

FIG. 3 is a graph showing the relation of lift vs. exciting currentduring opening an electro-magnetically driven valve for control ofexciting current depending upon a position of an armature in the valve.

FIG. 4A is a graph showing the change of an FB control gain dependingupon spacing distance (lift L) of an armature from electromagnets, whereit is shown that the FB control gain is set larger in a case that anactual moving speed is smaller than a target moving speed (ΔV<0) than ina case that an actual moving speed is larger than a target moving speed(ΔV>0).

FIG. 4B is a graph showing the change of an FB control gain dependingupon deviation ΔV of an actual moving speed from a target moving speed,wherein it is shown that the FB control gain is decreased as thedisplacement (lift) of an armature toward electromagnets increases.

FIG. 5 is a schematic diagram of a control system for implementingenergization control of an electro-magnetically driven valve in aninternal combustion engine of a vehicle in accordance with the presentinvention, but illustrating only elements relating to the control of thepresent invention.

FIG. 6 shows a flowchart of an embodiment of a basic structure ofenergization control of an electro-magnetically driven valve accordingto the present invention.

FIG. 7 shows a partial flowchart of the flowchart of FIG. 6 in a casethat learning modification is incorporated in the control; the partcorresponding to the modification is shown.

FIG. 8 shows a partial flowchart similar to that in FIG. 7.

FIG. 9 shows a partial flowchart similar to that in FIG. 8.

EXPLANATION OF PREFERRED EMBODIMENTS

FIG. 4A is a graph showing an embodiment according to the presentinvention, in which a target moving speed is set out for lift L duringopening of a valve and a FB control gain Gb is reduced with the increaseof the lift L, as illustrated in FIG. 2. As already noted, together withthe increase of the lift L, namely, as an armature is brought closer toelectromagnets, its electromagnetic force is increased and the variationof an exciting current fed to coils more largely varies theelectromagnetic force generated on the electromagnets. Accordingly, asthe armature is brought closer to the electromagnets, a contribution ofan FB control amount to the electromagnetic force or the moving speed ofthe armature is increased, and therefore, as shown in FIG. 4A, it ispreferable that the FB control gain Gb is progressively reduced as thearmature is brought closer to the electromagnets in order to avoid theoccurrence of control hunting.

Further, as seen from this figure, the FB control gain Gb is set smallerin a case that a deviation ΔV of an actual moving speed of the armaturerelative to its target moving speed is positive (ΔV>0) than in a casethat ΔV is negative (ΔV<0). In this regard, in each case of ΔV>0 andΔV<0, the FB control gain may be set as a constant, such as Gb_((ΔV<0))and Gb_((Δv>0)), where Gb_((ΔV<0))>Gb_((ΔV>1)). In this case, since ΔV=0upon the switching of the FB control gain, no abrupt change of the FBcontrol amount due to the switching of the FB control gain occurssubstantially. However, for canceling the deviation ΔV, the FB controlgain Gb may be varied substantially continuously with the deviation ΔV,in order that the deviation ΔV may disappear while preventing the abruptchange and control hunting. Accordingly, the FB control gain may begiven as a function of two parameters, lift L and deviation ΔV, whichfunction decreases with the increase of the lift L (see curves in FIG.4A and arrows in FIG. 4B) and varies depending upon the deviation ΔV(see arrows in FIG. 4A and FIG. 4B).

Moreover, in the illustrated embodiment, the FB control gain Gb may bemodified depending upon a force, applied to the valve body byoperational fluid controlled by the valve, in which the FB control gainis set smaller when the force acts on the valve body in the samedirection as its movement (P<0) than when the force acts on the valvebody in the direction opposite to its movement(P>0). In this connection,with respect to P, its magnitude in each of the opposite signs may betaken into account, and the setting curve based upon ΔV may be modifieddependent upon the value of P.

FIG. 5 is a schematic diagram of a control system for implementingenergization control of an electro-magnetically driven valve in aninternal combustion engine of a vehicle in accordance with the presentinvention, but illustrating only elements relating to the control of thepresent invention. In this internal combustion engine for a vehicle, acontrol of the operation of the engine is executed with a vehicleoperational control device. In the diagram, the vehicle operationalcontrol device 100 is a control device equipped with a microcomputer, towhich fed are a signal indicating an accelerator opening from anaccelerator opening sensor 1 which detects the depression of anaccelerator pedal by a driver; a signal indicating an engine speed froman engine speed sensor 2; a signal indicating a vehicle speed from avehicle speed sensor 3; a signal indicating a longitudinal accelerationof the vehicle from a longitudinal acceleration sensor 4; a signalindicating a temperature condition in the engine from an engine coolingwater sensor 5; a signal indicating an angular position of a crank shaftfrom a crank shaft angular sensor 6; a signal indicating an intake valveopening from an intake valve lift sensor 7 (designated by 40 in theexample of FIG. 1); and a signal indicating an exhaust valve openingfrom an exhaust valve lift sensor 8. The vehicle operational controldevice 100 determines how to operate the engine every moment based uponthe information, given from the above input signals relating to theoperational conditions of the engine, and controls the operations of athrottling valve 9 provided in an intake passage of the engine; fuelinjection valves 10, injecting fuel in intake air of the engine; anignition coil 11 activating ignition plugs of the engine; coils 12 forclosing the intake valve (designated by 303 in the example of FIG. 1);coils 13 for opening the intake valve (304 in FIG. 1); coils 14 forclosing an exhaust valve; and coils for opening the exhaust valve.

In the followings, a way of executing a method of controllingenergization of an electro-magnetically driven valve according to thepresent invention with a vehicle operational control device as shown inFIG. 5 will be more in detail explained with respect to one of itsembodiments. FIG. 6 is a flowchart showing the whole control steps inthe embodiment.

When control starts in response to closure of an ignition switch, notshown in the drawings, data are read-in in step 10. Then, in step 20, itis judged whether or not the valve, the object to be controlled, shouldbe opened, based upon the read-in data. If the answer is YES, thecontrol goes to step 30, in which it is judged whether or not lift L ofthe valve has reached to the full opened lift Lo. Until the valve isfully opened, the answer will be NO, and thus the control will go tostep 40.

In step 40, it is judged whether or not flag F1 is 1. In this type ofcontrol, since flag F1 has been reset to 0 at the starting of thecontrol, the answer is NO at the first time the control reaches to thisstep after starting of the control, and thus, the control goes to step50, in which calculated is a map, as illustrated in FIG. 2, defining therelation of lift L vs. target valve-opening speed Vt. In thisconnection, the relation of lift L vs. target valve-opening speed Vt iscalculated based upon a operational condition of the engine in everyevent of opening of an electro-magnetically driven valve, and thecalculation is executed based upon the signals from the respectivesensors as illustrated in FIG. 5. In this embodiment, since the judgmentof flag F1 in step 40 and the setting of flag F1 to 1 in step 60 areexecuted, the setting of the map is executed, at the beginning, once foreach of valve-opening events.

When the control reaches to step 70, current If, to be fed to thevalve-opening coils as the amount of FF control in the totalenergiazation amount is calculated, based upon the map of lift L vs.target valve-opening speed Vt, set in the previous step and a map oflift L vs. exciting current as illustrated in FIG. 3. Then, the controlgoes to step 80.

In step 80, a valve-opening speed V at a moment in each flow is comparedwith a target valve-opening speed Vt at the corresponding moment, andthe difference between them ΔV=V−Vt is calculated.

Next, the control goes to step 90, in which, based upon a judgment ofthe relation between the direction of operational fluid flow under thecontrol of the vehicle operational control device as illustrated in FIG.5 and the direction of the movement of the valve body (the sign of P inFIG. 4), FB control gain Gb for this moment is calculated using afunction Gb (L, ΔV, P) employing the above parameters as variables. Thefunction Gb(L, ΔV, P) in the calculation of the FB control gain isformed as shown in FIG. 4A or 4B, rendering the FB control gain largerfor larger distance between the armature and electromagnets attractingit (=Lo−L), and further, calculating the FB control gain which variesdepending upon ΔV and P in the above- mentioned manner.

Then, in step 100, based upon the above-calculated deviation ΔV and FBcontrol gain, current Ib, fed to the valve-opening coils as the amountof feedback control in the energization of the valve is calculated. Gbis defined as positive, so that Ib is calculated by Ib=−Gb·ΔV.

In the next step 110, the energization value for the valve-opening coilsis calculated by I=If+Ib. When ΔV>0, i.e. the actual moving speed of thearmature is larger than its target moving speed, the current componentof FB control Ib reduces the exciting current fed to the coils bysubtracting (the absolute value of) Gb·ΔV from the current component Ifof the FF control. On the other hand, when ΔV<0, i.e. the actual movingspeed of the armature is smaller than its target moving speed, thecurrent component of FB control Ib adds the absolute amount of Gb·ΔV tothe current component If of the FF control. As explained above, theabsolute value of Gb·ΔV is larger when ΔV is negative than when ΔV ispositive.

Subsequently, in step 120, current I, a sum of the current If,calculated as the current component of FF control, and the current Ib,calculated as the current component of FB control, is fed to thevalve-opening coils. In this connection, in the example of theenergization pattern of opening the valve based upon the FF control asillustrated in FIG. 3, when the valve is opened to about one-third of afull opened condition, the current for the coils is rapidly raised up toa high value 11, held to the value 11 for a while, and subsequently,reduced gradually to a low value 12 as the valve is rendered closer tothe full opened condition, and then fallen down to a holding currentwhen the valve is fully opened. The reason why no current is fed in theinitial phase of the opening of the valve is because, in this phase, thedistance between the armature and electromagnet to be energized is toolong for the electromagnetic force to effectively contribute to themovement of the valve. Accordingly, in the initial phase of opening ofthe valve, the armature is moved toward the full opened position underonly the action of the springs. In the initial phase of opening of thevalve, in the same way as the FF control, the FB control does noteffectively contribute to the movement of the armature, either. Thus,the FB control may be set to start after the armature moves by a certaindistance (it may be before the starting of feeding exciting current ofthe FF control).

In accordance with the above-described manners, a higher degree ofcontrol can be achieved, in which a vibration system, consisting of themass body including the armature, valve shaft connected thereto, valvebody, etc. and springs, is rendered vibrating, and the valve is openedand closed more rapidly using electromagnets having smaller capacities,while, when the armature rests on the electromagnets in the end of theopening and/or closing event of the valve and/or when the valve bodyrests upon the valve seat in closing the valve, the moving speeds of thearmature and valve body are brought as close to zero as possible.

Next, referring to FIGS. 7, 8 and 9, there is explained about anembodiment incorporating a function of learning modification asdescribed above by modifying a part of the flowchart in FIG. 6.

For executing learning modification, first, as shown in FIG. 7, thecontrol goes to step 51 in the way of going from step 40 to step 50,i.e. upon the staring of the valve-opening operation in this example,and it is judged whether or not a condition for learning modification isestablished, i.e. whether or not the engine is operated under conditionwhere the learning modification is allowed. Conditions that theoperation of the engine is not subject to the effect of the acceleratoropening and the force imparted on the valve body from operational fluidis constant, such as just before stopping the engine, during fuelcut-off, upon starting of the engine, etc., may be considered assatisfying conditions for the learning modification. Then, when theanswer is YES, the control goes to step 52, in which flag F2 is set to1.

Subsequently, as shown in FIG. 8, the control goes from step 120 to step130 before returning to step 10, in which it is judged whether or notflag F2 is set to 1, and, if the answer is YES, the control goes to step131, in which it is judged whether or not flag F3 is set to 1. Flag F3will be set to 1 when the control goes to step 134 as described below.Then, because the answer is NO when the control has not reached to step131 before, the control goes to step 132, in which it is judged whetheror not lift L reaches to Lo−ΔL, by ΔL before lift of the full openedposition, Lo. The value of ΔL is set to an appropriate value so as tograsp the entire deviation of the actual moving speed of the armaturefrom its target moving speed, for example, the magnitude of 10˜20% ofthe fill opened lift Lo. Until the answer in step 132 turns into YES,the control continues returning.

When the answer in step 132 turns into YES, the control goes to step133, in which the current deviation ΔV of the actual moving speed of thearmature from its target moving speed is memorized as ΔVo. Since, inthis time, the control goes to step 134 in which flag F3 is set to 1,the control after this goes from step 131 to Return while bypassing step132.

When the valve reaches to the full opened position because of theadvance of the control according to the flowchart of FIG. 6 and theanswer of step 30 becomes YES, the control goes to step 31 as shown inFIG. 9, in which it is judged whether or not flag F2 is set to 1. If thelearning condition is not established, the answer is NO and the controlterminates.

When F2 has been set to 1, the control goes to step 32, in which it isjudged whether or not the final value Ve of the actual moving speed ofthe armature is at or above a predetermined speed threshold Va. When theanswer is YES, the control goes to step 33, in which it is judgedwhether or not the deviation ΔVo memorized previously in step 133 is ator above a predetermined deviation threshold ΔVb. If the answer is YES,the control goes to step 34. When the control reaches to this step, thedeviation of the actual moving speed of the armature from the targetmoving speed is not lower than the predetermined deviation threshold,and the final speed of the movement of the armature is not lower thanthe predetermined speed threshold. Then, in step 34, learningmodification of the function Gb(L, ΔV, P) for calculating the FB controlgain is executed so as to increase the FB control gain.

When the answer in step 33 is NO, the control goes to step 35. When thecontrol reaches to this step, the deviation of the actual moving speedof the armature from its target moving speed is entirely lower than thepredetermined deviation threshold but the final speed of the movement ofthe armature is not lower than the predetermined speed threshold. Then,in step 35, the map of lift L vs. exciting current If (FIG. 3) isshifted through the learning modification based upon the final speed Veof the movement of the armature so as to reduce the FF control amountand thereby decreasing the moving speed at least around the end of themovement. In this connection, in those steps, in addition to thelearning modification for the FF control amount, learning modificationof the map of lift L vs. target valve-opening speed Vt as shown in FIG.2 may be executed, which will render the speed control more preciser andsmoother.

When the answer in step 32 is NO, the control goes to step 36. When thecontrol reaches to this step, the final value of the actual moving speedof the armature is lower than the predetermined speed threshold. Thus,in step 36, the map of lift L vs. exciting current is shifted throughlearning modification based upon the final speed Ve of the movement ofthe armature so as to increase the FF control amount for increasing themoving speed at least around the end of the movement. In thisconnection, in the same way as step 35, the learning modification may beexecuted for the map of lift L vs. target valve-opening speed Vt in step36, which will render the speed control more preciser and smoother.

It will be apparent that, while FIGS. 6˜9 explained above show thecontrol in opening the valve from the closed position, the control inclosing the valve from the opened position may be executed insubstantially similar manners with non-substantial changes, such asreplacing the judgment for opening the valve with the one for closingthe valve, defining lift L as a moving distance from the full openedposition to the full closed position, etc.

In the above, although the present invention is explained with respectto several embodiments, it will be apparent to implement other variousembodiments within the scope of the present invention.

1. A method of controlling energaization of an electro-magneticallydriven valve having electromagnets and an armature which is attracted tothe electromagnets and thereby moving a valve body to either of anopened position or a closed position, comprising: determining a targetmoving speed of the armature relative to the electromagnets dependentupon a spacing distance of the armature from the electromagnet;controlling at least a part of energization of the electro-magneticallydriven valve through a feedforward control so as to make an actualmoving speed of the armature relative to the electromagnets inconformity with the target moving speed while controlling at least theother part of the energization through a feedback control based upon adeviation of the actual moving speed from the target moving speed; inwhich a gain of the feedback control is changed based upon a relationbetween the actual moving speed and the target moving speed.
 2. A methodof controlling energaization of an electro-magnetically driven valvedescribed in claim 1, wherein the FB control gain is rendered smallerwhen a force of an operational fluid, controlled by theelectro-magnetically driven valve, acts on the valve body in the samedirection as the movement of the valve body than when a force of theoperational fluid acts in the opposite direction to the movement of thevalve body.
 3. A method of controlling energaization of anelectro-magnetically driven valve described in claim 1, wherein thefeedback control gain is rendered smaller when the actual moving speedis higher than the target moving speed than when the actual moving speedis lower than the target moving speed.
 4. A method of controllingenergaization of an electro-magnetically driven valve described claim 2,wherein, when a final value of the actual moving speed is smaller than apredetermined speed threshold, the energization amount of theelectromagnets is shifted through learning modification, therebyincreasing the moving speed depending upon the spacing distance.
 5. Amethod of controlling energaization of an electro-magnetically drivenvalve described in claim 1, wherein, when a deviation of the actualmoving speed from the target moving speed is not lower than apredetermined deviation threshold and a final speed of the movement ofthe armature is not lower than a predetermined speed threshold, thecalculation of the FB control gain is shifted to be increased throughlearning modification.
 6. A method of controlling energaization of anelectro-magnetically driven valve described in claim 1, wherein, when adeviation of the actual moving speed from the target moving speed isentirely not higher than a predetermined deviation threshold but a finalspeed of the movement of the armature is not lower than a predeterminedspeed threshold, the energization amount of the electromagnets isshifted through learning modification, thereby decreasing the movingspeed at least around the end of the movement.
 7. A method ofcontrolling energaization of an electro-magnetically driven valvedescribed in claim 1, wherein, the feedback control gain is controlledso as to vary continuously depending upon a deviation of the actualmoving speed from the target moving speed.
 8. A method of controllingenergaization of an electro-magnetically driven valve havingelectromagnets and an armature which is attracted to the electromagnetsand thereby moving a valve body to either of an opened position or aclosed position, comprising: setting a target moving speed of thearmature relative to the electromagnets dependent upon a spacingdistance of the armature from the electromagnet; controlling an actualmoving speed of the armature relative to the electromagnets to berendered in conformity with the target moving speed, in which thesetting of the target moving speed is modified through learningmodification based upon a deviation of the actual moving speed from thetarget moving speed.
 9. A method of controlling energaization of anelectro-magnetically driven valve described in claim 2, wherein thefeedback control gain is rendered smaller when the actual moving speedis higher than the target moving speed than when the actual moving speedis lower than the target moving speed.
 10. A method of controllingenergaization of an electro-magnetically driven valve described claim 2,wherein, when a final value of the actual moving speed is smaller than apredetermined speed threshold, the energization amount of theelectromagnets is shifted through learning modification, therebyincreasing the moving speed depending upon the spacing distance.
 11. Amethod of controlling energaization of an electro-magnetically drivenvalve described in claim 2, wherein, when a deviation of the actualmoving speed from the target moving speed is not lower than apredetermined deviation threshold and a final speed of the movement ofthe armature is not lower than a predetermined speed threshold, thecalculation of the FB control gain is shifted to be increased throughlearning modification.
 12. A method of controlling energaization of anelectro-magnetically driven valve described in claim 2, wherein, when adeviation of the actual moving speed from the target moving speed isentirely not higher than a predetermined deviation threshold but a finalspeed of the movement of the armature is not lower than a predeterminedspeed threshold, the energization amount of the electromagnets isshifted through learning modification, thereby decreasing the movingspeed at least around the end of the movement.
 13. A method ofcontrolling energaization of an electro-magnetically driven valvedescribed in claim 2, wherein, the feedback control gain is controlledso as to vary continuously depending upon a deviation of the actualmoving speed from the target moving speed.